Kids are back in school, so I have had time to re-start sorting my stamps.

2 quick questions about Mint precancels:
a) is there any specific market for them? (i.e. are there collectors who seek them out rather than just keeping whatever falls their way)
b) are they worth any premium?
oops, third question:
c) and following on from a) and b) ... is there any value beyond the aesthetic to maintaining the gum integrity on mint precancels? I am hinging most of my collection (the ones under 50c) and I keep finding 15c mint precancels. I'd rather save the mounts for the more valuable items -- but if I hinge the cheap-o mint ones, am I losing anything tangible?
Thanks!